UNIVERSITY  OF  CALIFORNIA 

COLLEGE    OF  AGRICULTURE 

BERKELEY,   CALIFORNIA 


AGRICULTURAL    EXPERIMENT    STATION 
E.  J.  WlCKSON,  Director 


CIRCULAR  NO.  38 

(August,  1908.) 


THE  ARGENTINE  ANT  IN   CALIFORNIA. 


BY 


C.  W.  WOODWOETH. 


A  pest  that  may  easily  prove  to  be  the  most  troublesome  insect  ever 
introduced  into  the  State  has  been  recently  discovered  in  our  midst. 
Specimens  of  this  insect  were  collected  about  a  year  ago  by  Mr.  J. 


Fig.  1.     The  Argentine  Ant,  greatly  enlarged.     The  actual  size  is  shown  in 

small  figure  below. 

Chester  Bradley,  at  that  time  an  assistant  in  the  Entomological  De- 
partment of  the  University  of  California.  The  species  was  not  recog- 
nized by  him  at  the  time  as  anything  unusual  and  only  within  the  last 
two  months  lias  the  presence  of  the  A  r-cnl^^anl   in  the  State  been 


known.  The  identification  of  the  insect  was  made  by  Professor  W.  M. 
Wheeler  of  the  American  Museum  of  Natural  History,  to  whom  these 
specimens  of  ants  collected  by  Mr.  Bradley  had  been  submitted  for 
identification.  Dr.  Wheeler  at  once  made  known  the  character  of  the 
insect  and  the  writer  has  just  returned  from  a  trip  east,  where  he 
con  suited  with  Mr.  Bradley  and  Dr.  Wheeler  and  then  proceeded  to 
Xew  Orleans  and  had  opportunity  to  study  the  insect  in  that  region, 
where  it  has  been  highly  injurious  for  a  number  of  years.  Professor 
E.  S.  G.  Titus,  who  was  the  representative  of  the  United  States  Divi- 
sion of  Entomology  to  study  the  pest  in  New  Orleans,  has  also  recently 
visited  with  me  one  of  the  infested  areas  in  this  State  and  verified  the 
insect  in  the  laboratory  and  field. 

The  exact  locality  of  the  collection  made  by  Mr.  Bradley  has  not 
been  determined.  It  was  supposed  by  him  to  be  Ontario,  but  very 
careful  examination  of  the  ants  of  that  district  has  been  made  without 
finding  this  species.  It  has  been  found  abundantly,  however,  in  the 
following  northern  localities,  East  Oakland,  Alameda,  San  Francisco, 
San  Jose,  Cupertino,  and  a  point  near  Campbell.  In  the  southern  part 
of  the  State  Prof.  H.  J.  Quayle  has  just  located  a  small  colony  in 
Los  Angeles  and  another  at  Azusa  and  a  third  at  Upland. 

The  Argentine  ant  is  primarily  troublesome  as  a  household  pest, 
but  in  Louisiana  it  has  also  proven  of  first  importance  in  the  sugar  cane 
fields,  and  in  the  orange  orchards.  The  writer  fears  that,  besides 
its  other  injurious  habits,  it  may  not  be  second  in  importance  from 
the  orange  grower's  standpoint  to  the  introduction  of  the  white  fly, 
to  which  attention  was  called  by  this  station  a  year  ago,  and  which 
seems  to  be  gradually  spreading  over  the  State.*  Of  course,  there 
is  a  possibility  that  the  insect  may  not  prove  equally  troublesome 
in  all  parts  of  California  on  account  of  our  peculiar  climate;  but,  on 
the  other  hand,  it  may  prove  even  more  troublesome  than  at  New 
Orleans.  Indeed,  Professor  Newell  of  the.  Louisiana  Crop  Pest  Com- 
mission, who  has  given  more  attention  to  a  careful  study  of  this  insect 
than  any  one  else,  expressed  to  me  his  belief  that  our  climate  would 
be  more  favorable  for  the  ant  than  that  of  Louisiana.  At  any  rate 
the  possibility  of  the  insect  becoming  a  pest  in  California  comparable 
to  the  work  it  has  already  done  in  Louisiana  should  cause  us  to  give 
the  matter  the  most  serious  consideration. 


*  Prof.  Titus  of  the  Utah  Agricultural  College  and  Special  Agent  of  the  U.  S. 
Division  of  Entomology,  teUs  me  that  while  not  particularly  looking  for  the  insect, 
lie  noted  the  presence  of  t^^^T>iite    Ply,  Aleurodes  citri,  in  Chico  and  Visalia. 


HISTORY   IN   OTHER    COUNTRIES. 

As  the  name  Argentine  ant  suggests,  the  insect  was  first  described 
from  the  Argentine  Republic.  It  is  common  also  in  Brazil  and  is 
doubtless  native  to  the  southern  part  of  South  America.  No  one  lias 
given  us  an  account  of  the  seriousness  of  the  insect  in  its  native 
country.  The  only  record  we  have  of  the  insect  in  other  countries  is 
its  presence  in  Madeira,  where  it  was  reported  as  long  ago  as  1898  to 
have  entirely  displaced  other  species  and  become  apparently  the  same 
sort  of  a  pest  which  it  has  proven  to  be  about  New  Orleans.  It  was 
noted  as  early  as  1891  along  the  wharves  in  New  Orleans,  where  the 
coffee  ships  from  Brazil  were  docked.  By  1895  another  region  five  or 
six  miles  up  the  river  was  noticed  to  be  infested.  In  1899  they  were 
already  present  at  Audubon  Park.  By  1904  Mr.  Titus  of  the  United 
States  Department  of  Agriculture,  who  was  the  first  to  give  us  a  full 
account  of  these  insects,  records  them  from  many  points  along  the 
railroads  leading  out  of  New  Orleans,  as  well  as  a  large  part  of  the 
town.  Professor  Newell  this  year  reports  them  as  occupying  fully 
five  thousand  square  miles  of  territory,  extending  from  New  Orleans 
southward  to  the  Gulf  of  Mexico ;  to  the  north  and  west  one  hundred 
and  eighty  to  two  hundred  miles;  and  east  beyond  the  boundary  of 
the  State ;  and  wherever  the  insect  has  become  abundant  it  has  proven 
itself  by  far  the  most  troublesome  species  of  ant,  and  has  practically 
driven  out  all  other  species.  The  spread  of  the  species  will  thus  be 
seen  to  be  rather  slow,  but  it  completely  occupies  all  the  territory  it 
infests. 

RELATION  TO  OTHER  INSECTS. 

Like  many  other  kinds  of  ants,  the  Argentine  species  is  very  much 
attracted  by  the  secretions  of  scale  insects  and  plant  lice.  Every  tree 
in  New  Orleans  and  adjacent  towns  is  continually  patrolled  by  these 
ants  and  there  seems  to  be  very  good  evidence  that  the  ants  care  for 
certain  of  these  insects  in  much  the  same  way  as  the  corn  root  aphis 
is  cared  for  in  the  Mississippi  Valley  by  the  common  ant  of  the  corn 
fields.  At  any  rate,  the  writer  has  repeatedly  noticed  ants  carrying 
mealy  bugs  and  other  insects  of  this  general  class,  and  it  is  well  known 
that  the  mealy  bug  so  injurious  to  sugar  cane  is  very  much  worse  where 
the  ant  is  abundant.  Exactly  the  same  habits  are  observable  in  the 
infested  districts  here  in  California.  Some  of  our  native  species  of 
ants  have  been  justly  accused  of  protecting  the  woolly  aphis,  and 
probably  scale  insects  have  been  defended  froimtheir  parasites  in  many 


instances.  In  this  Stale,  where  plant  lice  and  scale  insects  are  naturally 
so  injurious,  this  tendency  of  the  Argentine  ant  to  care  for  these  insects 
may  be  a  particularly  serious  feature  of  the  situation. 

Attention  has  already  been  directed  to  the  tendency  of  these  ants 
to  destroy  other  species  of  the  same  group.  Many  observers  have  noted 
the  battles  of  the  ant  in  Louisiana,  which  invariably  result  in  the  defeat 
of  t  he  other  species,  so  that  the  only  ant  now  found  in  the  houses  in  the 
infested  territory  is  this  imported  species.  As  far  as  our  observations 
have  gone  the  Argentine  ant  completely  destroys  all  native  ants  in  the 
infested  regions.  This  is  a  case  of  replacing  one  bad  pest  by  another 
still  worse.  There  are  a  few  cases,  however,  in  which  the  ant  has  been 
somewhat  of  a  benefit.  Professor  Newell  tells  me  that  one  reliable 
correspondent  reports  the  ants  as  having  entirely  destroyed  the  bed 
bugs  in  the  poorer  sections  of  New  Orleans,  and  the  very  annoying 
pests  known  in  the  south  as  chiggers  have  disappeared  in  the  neigh- 
borhood of  Audubon  Park,  apparently  on  account  of  the  presence  of 
the  ant.  These  slight  benefits,  however,  in  no  way  offset  the  damages 
done  by  this  pest. 

DAMAGE  TO   CITRUS  TREES. 

The  direct  attack  of  these  insects  upon  citrus  trees  is  a  matter  that 
can  not  be  other  than  of  the  highest  importance  to  California  growers. 
At  the  Lousiana  Experiment  Station  at  Audubon  Park  the  production 
of  oranges  was  entirely  prevented  this  year  through  the  attack  of  these 
insects  upon  the  opening  blossoms,  or  if  these  escape,  upon  the  young 
fruit  itself.  It  was  too  late  in  the  season  for  me  to  see  the  method  of 
attack  when  I  visited  New  Orleans,  but  as  described  to  me,  it  consists 
in  the  insect  simply  boring  into  the  center  of  the  bud  and  eating  or 
injuring  enough  of  the  substance  to  cause  its  destruction.  This  method 
of  attacking  the  blossoms  of  plants  is  not  by  any  means  confined  to 
oranges,  since  many  other  kinds  of  flowers  are  also  attacked.  The  ant 
has  entirely  destroyed  the  cut  flower  industry  in  New  Orleans.  In 
some  of  the  orchards  about  New  Orleans  numerous  methods  have  been 
tried  to  prevent  the  insects  climbing  the  trees,  but  even  as  effective 
a  barrier-  as  tree  tanglefoot  has  proven  effective  only  for  a  day  or  two. 
The  insects  soon  cross  the  bands  upon  particles  of  dust  or  upon  the 
dead  bodies  of  other  members  of  the  colonies.  There  is  a  possibility 
that  our  method  of  keeping  a  dry  mulch  on  the  surface  of  the  ground  in 
orchards  will  prevent  the  formation  of  burrows,  and  therefore  keep 
our  orchards  fairly  free  from  the  insects,  but  their  habit  of  nesting 
among  the  roots  of  trees,  and  that  of  traveling  long  distances  may 
enable  them  nevertheless  to  do  the  same  injury  here  as  in  Louisiana. 


HOUSEHOLD  PEST. 

It  is  primarily,  however,  as  a  household  pest  that  this  insect  has 
made  itself  dreaded  in  Louisiana.  No  insect  has  ever  given  the  people 
of  that  district  so  much  annoyance  and  no  insect  has  been  so  hard  to 
control  as  the  Argentine  ant.  It  has  fully  maintained  its  reputation 
in  the  infested  districts  here  in  California.  Its  habits  are  very  similar 
to  those  of  other  species,  but  its  ceaseless  wandering  and  small  size 
enable  it  to  seek  out  every  hiding  place,  and  whenever  food  is  found 
they  will  soon  be  swarming  in  countless  numbers. 

The  old  and  well-known  method  of  placing  the  legs  of  tables  in 
dishes  of  water  for  instance  is  of  no  avail  whatever  against  this  species 
of  ants,  since  the  slightest  accumulation  of  dust  on  the  surface  of  the 
water  furnishes  a  sufficient  bridge  over  which  the  ant  can  pass.  It  is 
a  very  general  feeder,  eating  anything  that  other  species  of  ants  attack, 
including  all  kinds  of  food  materials,  and  both  Professor  Titus  and 
Professor  Newell  report  cases  where  they  have  directly  attacked  infants 
in  a  most  distressing  manner,  and  are  capable  of  biting  severely  enough 
to  be  quite  a  nuisance  to  larger  human  beings. 

It  is  much  more  successful  than  any  of  our  native  species  in  ob- 
taining food.  Just  outside  of  the  infested  district  the  native  species 
are  normally  abundant.  An  area  which  would  afford  foraging  ground 
for  a  hundred  native  ants  is  infested  by  fully  ten  thousand  of  the 
Argentine  species. 

STORED  PRODUCTS. 

The  Argentine  ant  proves  very  annoying  in  warehouses  and  stores, 
as  well  as  in  residences.  Every  kind  of  food  product  seems  to  be 
attacked  by  these  creatures.  Fruits,  dry  and  fresh,  meal,  sugar,  etc., 
are  all  subject  to  attack,  and  the  impossibility  of  protecting  such 
products  from  attack  makes  it  unusually  exasperating. 

OCCURRENCE  IN  CALIFORNIA. 

We  already  have  numerous  species  of  ants  in  this  State.  The 
family  to  which  this  ant  belongs  is  distinguished  from  other  ants  by 
the  structure  of  the  fact,  shown  in  figure  2.  In  related  ants  the 
ridges  near  the  antennae  arise  from  the  upper  edge  of  the  clypeus. 
The  most  satisfactory  character  for  identification  of  the  Argentine  ant 
in  distinguishing  it  from  the  other  members  of  this  family  is  the  ar- 
rangement of  the  teeth,  shown  also  in  figure  2.  All  other  species  have 
some  other  arrangement.  The  Argentine  bears  the  name  Iridomyrmex 
humilis  Mayr.      One   other   member  of  this   genus  is   found   in   the 


Southern  States.     Other  species  occur  in  South  America,  in  southern 
Asia  and  Australia. 

Mor(  Information  Seeded. — We  are  far  from  certain  that  the  dis- 
tribution of  the  Argentine  ant  is  limited  to  the  localities  mentioned 
above.  It  would  be  very  desirable  to  know  at  the  earliest  possible 
moment  of  the  presence  of  the  insect  in  any  locality  because  of  the 
possibility  of  eradication.     Eradication  is  possible,  and  has  often  been 


2.     The  Argentine  Ant.     Face  view  showing  the  characteristic 
arrangement  of  the  teeth. 

accomplished  with  a  variety  of  insects  when  taken  soon  enough.  We 
would  like  to  suggest,  therefore,  that  specimens  of  ants  of  all  kinds  be 
sent  in  to  the  Experiment  Station  for  authentic  determination.  We 
will  be  very  pleased  to  examine  and  report  upon  all  such  material  sent. 
How  to  Send  Specimens. — Specimens  may  be  sent  through  the  mail 
if  enclosed  in  any  tight  receptacle.  We  would  suggest  for  this  purpose 
the  use  of  an  ordinary  gelatin  capsule.  These  can  be  obtained  at  any 
drug  store.  The  insects  can  be  collected  by  wetting  the  finger  and 
putting  it  quickly  over  the  ants,  and  before  they  can  untangle  them- 
selves they  can  be  enclosed  in  the  capsules.  Put  but  a  single  ant  in 
each  capsule,  but  collect  two  or  three  at  least  of  each  kind.  It  is  very 
desirable  to  have  a  considerable  number  because  of  the  danger  of  in- 
dividual specimens  being  damaged,  three  or  four  will  be  amply  suffi- 


cient.  If  more  than  one  kind  is  collected  keep  them  separate  and 
give  the  exact  locality  of  each.  The  capsules  may  be  enclosed  in  a 
small  box  and  mailed  to  the  Entomological  Department,  University  of 
California. 

LIFE  HISTORY. 

The  whole  life  history  of  the  Argentine  ant  has  not  yet  been  made 
out.  Professor  Newell  has  given  us  the  most  complete  account  of  these 
insects,  and  has  secured  a  splendid  lot  of  observations  which  he  will 
probably  publish  later.  As  far  as  his  studies  have  gone,  there  are  only 
three  forms  in  the  case  of  this  species ; — the  worker  ant,  which  is  the 
one  commonly  found  about  the  surface  of  the  ground,  and  the  only 
one  which  is  ordinarily  observed;  the  queen,  or  female  considerably 
larger  than  the  worker;  and  at  certain  seasons  there  are  often  a  con- 
siderable number  of  winged  males.  Young  winged  females  also  occur 
at  times  in  considerable  numbers.  These  soon  lose  their  wings  and 
become  the  ordinary  queens.  In  every  nest  there  will  be  found  a  great 
number  of  ants  in  the  early  stages.  The  eggs  and  very  young  ants 
are  often  stuck  together  and  are  handled  by  the  worker  ants  en  masse. 
Before  the  young  grubs  become  half-grown  they  will  be  cared  for  in- 
dividually. The  ants  are  continually  tending  these  young,  feeding 
them  from  day  to  day,  and  transporting  them  about  from  one  part  of 
the  nest  to  another  to  maintain  heat  and  moisture  conditions  most  satis- 
factorily, and  when  one  breaks  into  a  nest  he  will  observe  the  workers 
busy  trying  to  rescue  these  young  insects.  When  the  larvae  become 
full  grown  they  transform  into  a  pupal  stage  in  which  the  legs  and 
other  appendages  of  the  full  grown  insect  are  readily  seen,  but  which 
are  not  capable  of  movement.  This  ant  does  not  spin  a  cocoon  in  this 
stage  as  is  common  in  many  species.  Finally,  just  before  the  ant 
emerges  as  a  perfect  insect,  one  can  observe  the  color  of  the  eyes  and 
then  of  the  rest  of  the  body,  beginning  first  as  a  pale  brown,  but  before 
emergence  becoming  almost  as  dark  as  the  older  ants.  Previous  to  this 
time  the  insects  are  almost  pure  white. 

Xest  Habits. — The  Argentine  ant  is  a  persistent  nest  builder  and 
dius  burrows  everywhere.  The  nest,  however,  is  not  a  compact  affair, 
but  consists  simply  of  burrows  often  isolated  from  each  other,  often 
deserted  and  then  re-occupied,  and  there  is  not  the  sharp  distinction 
between  families  which  is  observed  among  so  many  ants.  Mother 
insects  may  be  dwelling  contentedly  together ;  indeed,  the  ants  of  one 
district  seem  to  form  one  large  family,  no  matter  how  many  burrows 
or  how  many  separate  establishments  may  be  founded. 


8 

Means  of  Distribution. — The  Argentine  ant  seems  to  be  continually 
on  the  move.  Nearly  everywhere  one  can  see  long*  caravans  of  ants 
occupied  in  transporting  the  young  from  nest  to  nest.  In  this  way 
after  a  colony  has  been  established  in  one  locality  it  can  spread  through- 
out the  surrounding  region,  though  the  rate  of  progress  of  course  will 
be  small.  There  are  no  data  whatever  to  enable  us  to  determine  exactly 
how  fast  they  might  go  by  this  means.  It  is  likely  however  that  they 
will  only  go  fast  enough  to  provide  for  increase  in  numbers.  They  will 
be  able  thus  to  completely  occupy  the  territory  invaded  and  the  move- 
ment can  be  considered  due  to  the  need  for  better  feeding  grounds.  At 
the  time  of  the  flight  of  the  winged  insects  it  is  possible  that  more  rapid 
extension  might  occur,  but  no  ants  are  strong  fliers,  and  it  is  not  likely 
that  they  would  make  such  progress  as  might  be  made  in  a  season  by 
the  ordinary  migrations  of  a  prosperous  colony.  The  distribution  from 
one  colony  to  another  distant  center  is  doubtless  always  brought  about 
by  artificial  means.  The  distribution  in  Louisiana  is  very  good  evidence 
along  this  line.  The  insects  are  found  in  great  abundance  along  the 
Mississippi  River  from  New  Orleans  southward,  where  they  were 
evidently  carried  by  drift  wood  in  which  they  had  established  them- 
selves, and  in  all  other  directions  simply  along  the  lines  of  the  railroad. 
The  habit  the  insect  has  of  constantly  moving  its  colonies  makes  it 
very  easy  for  a  colony  to  be  transported  in  toto,  having  established 
itself  in  some  box  of  merchandise.  Potted  plants  or  even  nursery  stock 
with  the  earth  balled  would  be  very  favorable  means  of  transportation 
of  small  colonies.  Its  introduction  to  California  was  very  likely  by 
rail,  and  it  is  likely  that  it  will  very  largely  follow  the  main  lines  of 
transportation  in  its  distribution  over  the  State.  As  far  as  we  are 
aware,  it  is  necessary  for  enough  of  a  colony  to  include  one  queen  at 
least,  to  be  transported  into  a  new  region  in  order  to  establish  itself. 
Because  of  its  habits,  however,  it  wrould  be  very  easy  to  have  this 
accomplished  since  the  colony  brought  into  a  region  would  be  very 
likely  to  remove  from  the  package  in  which  it  was  transported  and 
establish  itself  in  the  ground  in  its  new  home. 

REMEDIES  FOR  ANTS. 

There  are  a  great  many  remedies  suggested  and  in  use  for  the 
control  of  ants.  These  may  be  classed  in  three  categories :  first, 
destruction  of  colonies ;  second,  the  interposing  of  barriers ;  and  third, 
ant  proof  construction.  With  many  species  of  ants  the  destruction 
of  a  colony  is  not  a  difficult  matter,  the  nest  being  a  very  definite 
structure  with  only  a  few  openings,  and  housing  all  of  a  single  family. 


The  best  remedy  to  be  used  in  such  a  case  is  carbon  bisulfid,  and  a 
small  amount  of  this,  say  a  teaspoonful,  placed  in  an  ordinary  anl  \s 
nest,  especially  when  the  ground  is  not  too  dry,  will  result  usually  in 
the  death  of  the  whole  colony.  The  opening  at  the  surface  of  the 
ground  should  be  covered  tightly,  and  if  the  carbon  bisulfid  is  effec- 
tive, no  further  signs  of  the  colony  will  be  observed  beyond  a  few 
wandering  individuals  that  were  foraging  at  the  time  the  carbon  was 
applied.  These  are  relatively  short-lived,  and  soon  disappear.  This 
method  is  probably  the  best  that  can  be  followed  even  in  the  case  of  the 
Argentine  ant,  but  because  of  the  relative  great  numbers  of  queens  and 
the  innumerable  openings,  the  difficulty  of  destroying  these  ants  in 
any  region  becomes  very  much  greater  than  with  the  ordinary  species. 
Still  it  is  probable  that  colonies  in  the  ground  can  be  destroyed  in  this 
manner.  Where  colonies  occur  however  in  the  woodwork  of  houses  or 
the  other  buildings,  or  in  the  bark  or  rotten  places  in  tree  trunks,  as 
is  true  of  this  species,  the  problem  becomes  very  evidently  still  more 
difficult, 

Barrios. — Barriers  consist  of  substances  either  repellent  or  difficult 
of  passage.  Of  the  repellent  substances,  corrosive  sublimate  seems  to 
have  been  about  the  most  effective.  It  is  not  yet  known  exactly  why 
such  a  substance  should  be  repellent  to  ants,  but  it  has  proven  so  and 
is  fairly  effective  against  the  Argentine  species.  It  will  not  be  found 
to  be  completely  satisfactory  however.  Barriers  across  which  ants 
find  difficulty  in  passing'  are  water,  vaseline  and  tanglefoot,  either  of 
which  is  completely  effective  as  long  as  its  surface  remains  clean;  but 
dust  particles  or  dead  bodies  of  other  ants  will  in  each  case  finally  form 
a  bridge  over  which  the  insects  can  pass,  They  are,  however,  suffi- 
ciently effective  to  be  extremely  useful,  as  a  control  measure  and  will 
be  found  very  efficient  for  our  common  larger  species,  but  least  effective 
against  the  Argentine  ant  of  all  the  ants  occurring  in  this  country. 

Ant  Proof  Construction. — Of  course  this  is  the  best  solution  of  the 
problem.  AVhere  ants  cannot  be  eradicated  all  containers  of  food 
material  should  be  made  ant  tight  in  every  region  where  ants  are 
troublesome.  This  is  something  that  is  quite  possible  even  for  single 
rooms  or  dwelling  houses,  though  it  will  require  very  different  methods 
from  those  which  are  in  vogue  in  ordinary  residence  construction. 
These  ants  do  not  burrow  in  wood  but  live  in  cracks  or  in  rotten  wood. 
The  important  thing  of  course  is  to  see  to  it  that  no  cracks  through 
which  ants  can  come  are  allowed  to  remain.  In  wooden  houses  this 
can  be  accomplished  by  a  free  use  of  putty  and  paint,  and  special  pro- 
visions about  the  openings  such  as  windows  and  doors,  and  by  constant 


10 

attention  to  any  cracks  that  may  form  through  the  drying  or  warping 

of  the  wood.     In  the  case  of  warehouses  the  use  of  concrete  as  far  as 
possible  is  thoroughly  to  be  recommended,  since  this  is  fairly  free  from 
danger  of  cracking  in  a  way  to  admit  ants.     The  most  serious  difficulty 
"in  ant   proof  construction  is  the  impossibility  of  free  ventilation. 

SUGGESTIONS  FOR  ERADICATION. 

From  what  has  been  said  above  it  will  be  seen  that  the  control  of 
this  species  of  ant  is  particularly  difficult  and  it  would  seem  therefore 
a  very  wise  policy  at  the  present  time,  while  the  species  has  such  a 
limited  distribution,  to  entirely  eradicate  it.  If  this  is  undertaken, 
however,  it  should  be  with  the  appreciation  of  the  fact  that  the  work 
involved  is  very  great  even  for  a  small  colony,  because  in  eradication 
work  only  the  last  individual  queen  insect  is  of  any  importance.  The 
simple  reduction  of  numbers  will  not  justify  the  effort  that  would  be 
put  forward. 

The  first  work  that  should  be  done  towards  eradication  is  to  find 
a  practical  means  of  limiting  the  spread  from  the  existing  colonies. 
Perhaps  a  water  barrier  reinforced  with  oil  may  prove  most  feasible, 
but  much  experimental  work  should  at  once  be  provided  for  to  de- 
termine the  wisest  procedure. 

The  next  step  would  be  naturally  the  attempt  to  destroy  all  the 
nests  in  one  of  these  areas.  Carbon  bisulfid  is  the  most  promising 
means  to  use,  but  here  again  experimental  work  might  result  in  the 
discovery  of  more  efficient  means.  When  these  two  steps  are  success- 
fully taken  the  remainder  of  the  work  is  but  the  continuance  of  the 
campaign  along  these  lines. 

HOW  THIS  WORK  MAY  BE  DONE. 

There  is  no  legal  authority  in  the  State  whose  duties  would  include 
the  eradication  of  a  household  pest  unless  it  be  in  those  counties 
having  County  Entomologists,  whose  duties  are  whatever  the  Super- 
visors creating  these  offices  direct.  As  a  fruit  pest,  however,  it  falls 
in  the  domain  of  the  State  Commissioner  of  Horticulture  and  of  the 
County  Boards.  The  laws,  however,  creating  these  offices — while 
granting  abundant  authority  and  originally  designed  to  meet  just  such 
emergencies — nevertheless  fail  to  provide  the  necessary  means  and 
facilities  for  investigation  which  must  first  be  made  when  a  new  kind 
of  pest  is  introduced  before  effective  work  can  be  done  and  which 
must  accompany  the  work  in  most  cases  as  long  as  it  is  under  way. 


11 

If  anything-  is  to  be  done  at  all  it  requires  therefore  that  public- 
spirited  citizens  interest  themselves  in  the  matter  and  see  that  the 
machinery  of  government  by  which  emergencies  are  met  be  set  in 
motion. 

It  should  be  understood  that  the  whole  State  is  interested  in  this 
matter,  and  not  simply  the  communities  where  the  insect  is  now  present. 
There  is  no  reason  to  expect  this  insect  to  spread  in  this  State  less 
rapidly  than  in  Louisiana,  and  if  that  is  accomplished  the  insect  will 
be  infesting  the  homes  of  ninety  percent  of  the  population  of  the  State 
within  ten  years.  If  one  community  destroys  the  insects  in  its  midst 
it  stands  in  continuous  danger  of  becoming  re-infested,  thus  necessitat- 
ing doing  the  work  over  again.  Thus  far  the  insect  is  practically 
confined  to  towns.  For  many  years  this  was  true  in  Louisiana.  The 
ants  spread  very  slowly  through  the  towns,  infesting  block  after  block, 
coming  to  the  towns  in  shipments  by  rail  or  boat  and  only  spreading 
into  the  country  after  completing  the  infestation  of  the  towns.  Now 
they  are  beginning  to  appreciate  the  danger  to  their  cane  and  orange 
crops  after  five  thousand  square  miles  of  territory  are  infested  and  the 
insect  has  spread  into  an  adjacent  State.  Here  there  is  probably  less 
than  five  square  miles  of  infested  territory.  The  people  in  the  infested 
districts  are  ready  and  anxious  to  do  anything  that  might  be  necessary 
to  rid  themselves  of  the  pest,  but  there  is  nothing  that  they  can  do 
individually  except  little  palliative  measures  that  leaves  the  great 
menace  to  the  State  at  large  unaffected. 

If  eradication  is  not  accomplished,  besides  the  financial  losses  to 
Horticulturists,  the  majority  of  the  inhabitants  of  the  State  must 
expect  in  a  few  years  at  most  to  have  hundreds  of  these  insects  patrol- 
ing  their  homes  from  cellar  to  garret,  day  and  night,  winter  and 
summer. 


